The present invention relates to an ultrasonic treatment apparatus capable of treating an organism with use of frictional heat produced by ultrasonic vibration while grasping the organism.
Conventionally, there are various ultrasonic treatment apparatuses that are used to carry out treatments, such as incision, coagulation, etc., by utilizing the energy of ultrasonic vibration. Among these apparatuses, one that is designed to grasp an organism as it treats it by means of ultrasonic vibration is described in U.S. Pat. No. 5,322,055, for example.
This ultrasonic treatment apparatus comprises a long sheath for use as an insert section. A jaw, a grasping member, is rockably attached to the distal end of the sheath. A vibration transmitting member for transmitting ultrasonic vibration is passed through a first channel that is formed in the sheath. The distal end portion of the transmitting member projects from a distal-end opening of the sheath so as to face the jaw, and serves as an ultrasonic probe that grasps an organism in conjunction with the jaw and treats it by means of ultrasonic vibration.
The jaw is connected to an operating rod that is passed through a second channel in the sheath. As the rod is pushed or pulled, the jaw is rocked between a closed position in which it faces and engages the ultrasonic probe and an open position in which it is separated from the probe.
A mechanism for pushing and pulling the operating rod is provided in an operating section that is situated on the proximal end side of the sheath. More specifically, the operating section is provided with a fixed handle, which is formed integrally therewith, and a movable handle that is rockably attached to the operating section (fixed handle) by means of a pivot. As the movable handle is rocked, the operating rod connected thereto is pushed or pulled. The pivot, a fulcrum for the rocking motion of the movable handle, is situated between a finger plate portion of the movable handle, which serves as a point of application to which an operating force is applied, and a point of action or input portion (junction between the operating rod and the movable handle) for the operating force on the rod. In consideration of the operating efficiency, the jaw is designed to be closed as the movable handle is gripped and moved forward or toward the fixed handle.
Since the ultrasonic probe is formed of the free end of the ultrasonic vibration transmitting member, it is pushed and deflected by the jaw as the organism is held between the probe and the jaw. Accordingly, a gap or noncontact space is formed between the probe and the jaw, so that the coagulation-incision capacity of the apparatus is lowered.
In one case, the jaw is rocked to its closed position by pushing out the operating rod forward. In the other case, it is done by pulling the rod. In the former case, the jaw and the operating rod are connected to each other in a position above a fulcrum for the rocking motion of the jaw or outside the sheath. In the latter case, the jaw and the rod are connected in a position below the fulcrum or inside the sheath. In the latter case, however, a pivot as the fulcrum for the rocking motion of the jaw is inevitably situated on the outer peripheral side portion of the sheath, so that the jaw and the distal end portion of the sheath that supports the jaw cannot maintain high strength and durability. According to the technique described in U.S. Pat. No. 5,322,055, therefore, the jaw is designed to be closed by pushing out the operating rod forward, so that the pivot for the jaw is situated inside the sheath, whereby the strength and durability of the jaw and the distal end portion of the sheath are maintained. In this arrangement, however, the pivot as the fulcrum for the rocking motion of the movable handle is situated between the finger plate portion of the movable handle, which serves as the point of application to which the operating force is applied, and the point of action or input portion for the operating force on the rod. Further, the operating rod is moved forward to close the jaw in a manner such that the movable handle is gripped and moved forward or toward the fixed handle. It is necessary, therefore, to provide a link mechanism for aligning the operating direction for the movable handle with the moving direction of the operating rod. Thus, when the movable handle (finger plate portion) is moved forward, the point of action, which is situated on the opposite side of the fulcrum for the rocking motion of the movable handle from the finger plate portion, moves rearward. Accordingly, it is necessary to provide a link mechanism for converting this rearward movement into a forward movement and transmitting the forward movement to the operating rod. With use of the link mechanism of this type, frictional resistance is produced at the fulcrum of the link and each end of the link by the transmission of force. As the number of kinematic pairs is increased, moreover, regions that require necessary gaps for operation increase, so that backlash enlarges as a whole. As the number of required members increases, furthermore, regions that are subject to elastic deformation also increase, so that various problems are aroused including an increase in the general elastic deformation.
Further, the outer peripheral surface of the vibration transmitting member is provided with a plurality of support pieces that are located corresponding individually to nodes in the ultrasonic vibration. These support pieces serve to hold the transmitting member in the central portion of the first channel and prevent the transmitting member from touching the first channel. If the organism is held between the jaw and the distal end portion of the transmitting member in a manner such that the operating rod is operated to rock the jaw, however, the distal end portion of the transmitting member that is not supported by the support pieces is deflected by a force received from the jaw. In some cases, therefore, the lateral portion of the distal end of the transmitting member that is situated in the sheath may come into contact with the first channel. If the distal end portion is subjected to a substantial lateral force for any reason or other, it is deflected, so that the lateral portion of the distal end of the transmitting member inevitably touches the first channel. In this case, frictional heat is produced as the deflected transmitting member comes into contact with the first channel. Thereupon, some of the vibration energy is wasted in the region concerned, and the temperature of the sheath surface increases. According to U.S. Pat. No. 5,322,055, therefore, receiving members for receiving the deflection of the lateral portion of the distal end of the transmitting member are provided corresponding individually to the leading node of the ultrasonic vibration and a second node next to it. Since the receiving member that is situated corresponding to the second node is formed of an elastic material, however, it is easily deformed in response to the deflection of the transmitting member. Thus, the deflection of the transmitting member cannot be restrained effectively. Accordingly, a gap is formed between the distal end portion of the vibration transmitting member and the jaw, so that the organism cannot be firmly held between them. In consequence, the organism cannot be treated securely.
Further, both the operating rod and the second channel penetrated thereby have a circular cross section. If the rod and the second channel are thus formed having the same sectional shape, the diameter of the second channel must be increased in order to form a gap for cleaning between the rod and the second channel. (If the rod is too thin, the operating force cannot be satisfactorily transmitted to the jaw.) If the diameter of the second channel (gap between the operating rod and the second channel) is enlarged, however, two problems are aroused. First, the operating rod buckles due to the presence of the gap between the rod and the second channel as the rod is pushed forward in the second channel. The other problem is that if the diameter of the second channel is increased in the case where the first and second channels are arranged in the sheath having a limited size, the diameter of the first channel that is penetrated by the vibration transmitting member must be reduced inevitably, so that the diameter of the transmitting member cannot be large enough to secure satisfactory strength. If the diameter of the second channel is reduced in order to avoid these problems, on the other hand, the gap between the operating rod and the second channel cannot be wide enough, so that it is hard to clean the interior of the second channel. In general, moreover, the distal end portion of the vibration transmitting member has a flat or columnar shape, and a grasping surface of the jaw, which is designed to grasp an organism in cooperation with the distal end portion, is flat. In some cases, therefore, the distal end portion of the transmitting member and the jaw may fail to hold the organism in a stable state between them. In the ultrasonic treatment apparatus described in U.S. Pat. No. 5,322,055, moreover, the flat grasping surface of the jaw is formed having V-shaped notch. If the distal end portion of the vibration transmitting member is eccentric or skewed in this case, however, the state of its contact with the grasping surface of the jaw varies to change the state of the grasped organism when the transmitting member is rotated. Thus, a gap is inevitably formed between the distal end portion of the transmitting member and the grasping surface. In some cases, therefore, the organism may not be able to be accurately treated in a desired state.